FIG. 1 illustrates a structure cross-sectional view of a conventional optoelectronic device 1. As shown in FIG. 1, the optoelectronic device 1 comprises a substrate 11 and a plurality of semiconductor layers 10, 12, 14, 16, 18 formed on the substrate 11, wherein the plurality of semiconductor layers 10, 12, 14, 16, 18 is sequentially grown on the substrate 11, and lattice constants of the semiconductor layers 10, 12, 14, 16, 18 gradually decrease along a thickness direction from the semiconductor layer 10 to the semiconductor layer 18. When a semiconductor layer having a smaller lattice constant, such as the semiconductor layer 12, is grown on a semiconductor layer having a larger lattice constant, such as the semiconductor layer 10, a tensile stress is formed between the semiconductor layer 10 and the semiconductor layer 12, and the tensile stress is not easily released. After the semiconductor layer 10 and the semiconductor layer 12 are formed, when the semiconductor layers 14, 16, 18 are grown on the semiconductor layer 12, the tensile stress is continually accumulated in the optoelectronic device 1, then defects or dislocations are formed. FIG. 2 illustrates an SEM diagram of a cross-sectional view of the conventional optoelectronic device 1. When the plurality of semiconductor layers 10, 12, 14, 16, 18 is sequentially grown on the substrate 11, the tensile stress induces large amount of defects or dislocations, and the defects or dislocations, as marked by y in FIG. 2, are continually accumulated along a thickness direction of the semiconductor layer as marked by a direction of an arrow Y in FIG. 2